/*

 * Licensed to the Apache Software Foundation (ASF) under one

 * or more contributor license agreements.  See the NOTICE file

 * distributed with this work for additional information

 * regarding copyright ownership.  The ASF licenses this file

 * to you under the Apache License, Version 2.0 (the

 * "License"); you may not use this file except in compliance

 * with the License.  You may obtain a copy of the License at

 *

 *     http://www.apache.org/licenses/LICENSE-2.0

 *

 * Unless required by applicable law or agreed to in writing, software

 * distributed under the License is distributed on an "AS IS" BASIS,

 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.

 * See the License for the specific language governing permissions and

 * limitations under the License.

 */

package com.bff.gaia.unified.runners.fnexecution.state;



import com.bff.gaia.unified.model.fnexecution.v1.UnifiedFnApi.StateRequest;

import com.bff.gaia.unified.model.fnexecution.v1.UnifiedFnApi.StateResponse;



import java.util.concurrent.CompletionStage;



/**

 * Handler for {@link com.bff.gaia.unified.model.fnexecution.v1.UnifiedFnApi.StateRequest StateRequests}.

 */

public interface StateRequestHandler {

  /**

   * Handle a {@link com.bff.gaia.unified.model.fnexecution.v1.UnifiedFnApi.StateRequest} asynchronously.

   *

   * <p>The handler is allowed to complete the future within the callers thread if it can be

   * completed without blocking. Otherwise the caller should delegate to another thread to perform

   * any blocking work completing the future when able.

   *

   * <p>Throwing an error during handling will complete the handler result {@link CompletionStage}

   * exceptionally.

   */

  CompletionStage<StateResponse.Builder> handle(StateRequest request) throws Exception;



  static StateRequestHandler unsupported() {

    return request -> {

      throw new UnsupportedOperationException(

          String.format("Cannot use an empty %s", StateRequestHandler.class.getSimpleName()));

    };

  }

}